Change scheme to widen toplevel private

Doing it while desugaring does not always work since definitions
might already have been indexed before desugaring happens, in which
case the symbol gets duplicated. We do the widening in Namer instead.

Author: odersky

compiler/src/dotty/tools/dotc/ast/Desugar.scala

@@ -1047,13 +1047,7 @@ object desugar {
     else {
       val sourceName = ctx.source.file.name.takeWhile(_ != '.')
       val groupName = (sourceName ++ str.TOPLEVEL_SUFFIX).toTermName
-      val widenedStats = nestedStats.map {
-        case stat: MemberDef if stat.mods.is(Private) =>
-          stat.withMods((stat.mods &~ Private).withPrivateWithin(pdef.pid.name.toTypeName))
-        case stat =>
-          stat
-      }
-      val grouped = ModuleDef(groupName, Template(emptyConstructor, Nil, Nil, EmptyValDef, widenedStats))
+      val grouped = ModuleDef(groupName, Template(emptyConstructor, Nil, Nil, EmptyValDef, nestedStats))
       cpy.PackageDef(pdef)(pdef.pid, topStats :+ grouped)
     }
   }

compiler/src/dotty/tools/dotc/typer/Namer.scala

@@ -310,6 +310,15 @@ class Namer { typer: Typer =>
         else name
     }
 
+    /** If effective owner is a package `p`, widen `private` to `private[p]` */
+    def widenToplevelPrivate(sym: Symbol): Unit = {
+      var owner = sym.effectiveOwner
+      if (owner.is(Package)) {
+        sym.resetFlag(Private)
+        sym.privateWithin = owner
+      }
+    }
+
     /** Create new symbol or redefine existing symbol under lateCompile. */
     def createOrRefine[S <: Symbol](
         tree: MemberDef, name: Name, flags: FlagSet, infoFn: S => Type,
@@ -325,6 +334,8 @@ class Namer { typer: Typer =>
           prev
         }
         else symFn(flags, infoFn, privateWithinClass(tree.mods))
+      if (sym.is(Private))
+        widenToplevelPrivate(sym)
       recordSym(sym, tree)
     }
 

tests/neg/toplevel-privates/A.scala renamed to tests/neg/toplevel-privates/A_1.scala

@@ -1,10 +1,10 @@
-package p22
+package p
 
 private val x = 10
 
 val y = x
 
-private[p22] val xx = 10
+private[p] val xx = 10
 
 val yy = xx